Various systems and apparatus have been developed to sterilize lumen devices, such as endoscopes and other devices having a lumen. Methods of sterilizing lumen devices may utilize a sterilization chamber and one or more gaseous sterilants, such as ozone or vaporized hydrogen peroxide (VHP). In order to achieve effective sterilization, all contaminants within the lumen device must be exposed to the gaseous sterilant, including contaminants suspended in the air within the lumen device and contaminants on interior and exterior surfaces of the lumen device. However, the length of a lumen is many times greater than its diameter and such geometry can make it difficult to penetrate the lumen (i.e., interior passageway) with a gaseous sterilant.
Known methods for sterilizing a lumen cause a gaseous sterilant to flow through the lumen by creating a difference in pressure across the length of the lumen (i.e., pressure drop). Existing apparatus and methods used to create adequate pressure drop across the length of a lumen have various drawbacks. Such drawbacks include complexity, limitations on the types of devices that can be sterilized, and possible recontamination of the lumen when the gaseous sterilant is withdrawn from the lumen.
One prior art method for creating a pressure drop to sterilize lumen devices utilizes an expansion tank disposed within a sterilization chamber. A first end of a lumen is fluidly connected to the expansion tank, and a second end of the lumen is open to the sterilization chamber. In this respect, the lumen fluidly connects the expansion tank with the sterilization chamber. The volume of the expansion tank is such that all of the unsterile air contained within the lumen can be forced into the expansion tank during the sterilization cycle. The purpose of the expansion tank is to provide a chamber that will be at a lower pressure than the sterilization chamber, and thus “draw” gaseous sterilant through the lumen.
An expansion tank is used in a sterilization process in the following manner. First, a vacuum is drawn on the sterilization chamber, and the pressures within the sterilization chamber and the expansion tank are allowed to equalize. Next, a gaseous sterilant is introduced into the sterilization chamber. Thereafter, the pressure of the sterilization chamber is allowed to rise above the pressure in the expansion tank. The resulting difference in pressures between the sterilization chamber and the expansion tank causes the gaseous sterilant to flow through the lumen and into the expansion tank. The gaseous sterilant will continue to flow into the expansion tank until the pressure in the sterilization chamber and the pressure in the expansion tank have equalized, and the concentration of the sterilant is at a desired level. After a suitable period, a vacuum is again drawn on the sterilization chamber, thereby removing the gaseous sterilant from the sterilization chamber. As the pressure decreases within the sterilization chamber, the gaseous sterilant is drawn out of the expansion tank through the lumen and into the sterilization chamber. After the pressure drops to a desired level, a second gas (e.g., air) is introduced into the sterilization chamber to purge the remaining gaseous sterilant using an analogous series of steps.
Various problems may be encountered when using prior art expansion tanks to sterilize lumen devices. One problem is inadequate sterilization caused by the presence of unsterile air within the expansion tank and the lumen. In this regard, some unsterile air may remain within the lumen after a vacuum has been drawn on the sterilization chamber. When a gaseous sterilant is introduced into the lumen, the remaining unsterile air may be pushed ahead of the gaseous sterilant through the lumen and into the expansion tank. The unsterile air poses a problem because it does not actively mix with the gaseous sterilant, due to nonturbulent flow (i.e., plug flow). It is possible for the sterilant to penetrate unsterile air without active mixing by gas diffusion. However, gas diffusion is a slow process, and does not insure that all contaminates are adequately exposed to the gaseous sterilant. Accordingly, the unsterile air can contain viable organisms that survive the sterilization process. The surviving viable organisms may be subsequently drawn back into the lumen as gas is withdrawn from the sterilization chamber. The surviving viable organisms can then compromise sterility of the lumen device by re-depositing in the lumen.
The present invention overcomes the above-mentioned drawbacks and others associated with prior art systems for sterilization of lumen devices.